Mixopterus
| Mixopterus Temporal range: Late Silurian,
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| Fossil of M. kiaeri | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Order: | †Eurypterida |
| Superfamily: | †Carcinosomatoidea |
| Family: | †Mixopteridae |
| Genus: | †Mixopterus Ruedemann, 1921 |
| Type species | |
| Mixopterus multispinosus Ruedemann, 1921
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| Other species | |
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Mixopterus was a genus of Late Silurian eurypterid. It is classified as part of the family Mixopteridae, along with the closely related genus Lanarkopterus.
Description
Mixopterus was characterised by a robust exoskeleton with scattered tubercles or semicircular scales. The prosoma (head) was subquadrate, protruding antemedially. The chelicerae (claws in front of the mouth) were small.[1]
The two first pairs of legs of Mixopterus (appendages II and III) were highly specialized and not used for walking, instead being highly developed with long paired spines.[1] The two following pairs (appendages IV and V) were moderately sized and typically spiniferous walking legs. The last legs, (VI), form a pair of swimming legs characteristic of the Eurypterida.[2]
Mixopterus preserves a long ventro-medially placed genital appendage.[2] The preabdomen, the front portion of the body, was narrow with axial furrows, while the postabdomen was narrow. The telson was a curved spine.[3]
Ichnology and movement
Tracks attributed to Mixopterus have been discovered in fossil deposits in Ringerike, Norway. The tracks, referred to the ichnogenus Merostomichnites, were made by an arthropod in which only three pairs of legs took part in the gait, the last pair being swimming legs.[2]
Swimming legs that constitute the last limbs of the prosoma are present in eurypterine eurypterids, out of which the only reasonably large taxa present in the silurian deposits of Ringerike are Mixopterus kiaeri and Pterygotus holmi. With its slender and spinless walking legs and short genital appendage, Pterygotus could not have produced the tracks, though they match the size and morphology of M. kiaeri rather well. The great morphological similarities as well as the relative abundance of M. kiaeri in the region prompted Hanken and Størmer (1975)[2] to refer the tracks to Mixopterus.
Species
Mixopterus contains three valid species, with some others that historically have been assigned to it being recovered as outside of the genus. The species currently seen as valid species of the genus are:
- Mixopterus kiaeri Størmer, 1934 - Ringerike, Norway (Silurian)
- Mixopterus multispinosus Clarke & Ruedemann, 1912 - New York (Silurian)
- Mixopterus simonsoni Schmidt, 1883 - Saaremaa, Estonia (Silurian)
Invalid or reassigned species are listed below:
- Mixopterus dolichoschelus Peach and Horne, 1899 - Lanarkshire and Ayrshire, Scotland (Silurian), reclassified as its own genus, Lanarkopterus.[4]
See also
References
- ^ a b Euan Neilson Kerr Clarkson (1998). "Arthropods". Invertebrate Palaeontology and Evolution (4th ed.). Wiley-Blackwell. pp. 348–405. ISBN 978-0-632-05238-7.
- ^ a b c d Hanken, N.-M. & Størmer, L. (1975): "The trail of a large Silurian eurypterid". Fossils and Strata, No. 4, pp. 255-270, Pl. 1 -3.
- ^ Leif Størmer (1955). "Merostomata". Part P Arthropoda 2, Chelicerata. Treatise on Invertebrate Paleontology. pp. 34–35.
- ^ Ritchie, Alexander (1968-12-01). "Lanarkopterus dolichoschelus (Størmer) gen. nov., a mixopterid eurypterid from the Upper Silurian of the Lesmahagow and Hagshaw Hills inliers, Scotland". Scottish Journal of Geology. 4 (4): 317–338. doi:10.1144/sjg04040317. ISSN 0036-9276.
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| Notable genera | ||
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